Inkjet printing mechanisms, such as printers, may use print cartridges which shoot drops of liquid colorant, referred to generally herein as “ink,” onto a print medium, such as a page of paper. Each print cartridge may have a printhead formed with very small nozzles through which the ink drops are fired. To print an image, the printhead, or a printhead carriage supporting the printhead, may be propelled back and forth across the page along a printhead carriage rod, shooting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may be implemented in a variety of different ways, such as by piezo-electric or thermal printhead technology.
To enhance print quality, smooth motion of the printhead carriage along the carriage rod may be desired. However, during printing the carriage rod may become fouled with contaminants such as dust, ink aerosol particles, and print media particulate matter such as paper fibers. Such contaminants may interfere with smooth motion of the printhead carriage, thereby reducing print quality. The contaminants may cause friction between the printhead carriage and the carriage rod, thereby increasing strain on printer motors. The contaminants may also damage the printhead carriage or the carriage rod, thereby reducing the working life of the printer.
To clean and lubricate the carriage rod a lubricating pad, in the shape of a closed loop or a “doughnut”, may be frictionally fit around a circumference of the carriage rod. An inner diameter of the closed pad may be made smaller than the outer diameter of the carriage rod to ensure intimate contact of the closed pad with the sliding surface of the rod so that lubricating fluid is imparted thereto. The lubricating pad may lubricate and clean around the entire circumference of the carriage rod as the closed pad is moved therealong. However, the tight fitting closed pad may impart a large drag to the printhead carriage thereby straining printer motors and inhibiting accurate movement of the printhead carriage. Moreover, slight variations in the diameters of different closed pads may result in different drag sensitivities of pads on different carriage rods, thereby reducing consistency in print quality between similarly produced printers. The doughnut shaped closed pad which completely encircles the carriage rod may require the carriage rod to be end-supported, which may facilitate vibration of the carriage rod during use. Such vibration may cause positional errors and print quality defects of the printhead.